1. Field of the Invention
This invention relates to improved alumina or alumino-silicate refractories for lining aluminum-melting furnaces.
2. Description of the Prior Art
The linings of aluminum-melting furnaces are subject to erosion, corrosive attack, and undesirable adherence by the molten metal and dross held in such furnaces. Most non-phosphate bonded high alumina refractories have exhibited poor resistance to molten aluminum penetration. Phosphate-bonded high alumina refractories, in both burned and unburned forms, have been used with some success to line aluminum-melting furnaces. Although these linings have generally good resistance to metal penetration, after extended periods or when subjected to high temperatures they show metal penetration and excessive metal and dross adherence. The metal and dross adherence reduces furnace capacity and is difficult to remove by cleaning.
Attempts to improve the properties of high alumina refractories for lining aluminum-melting furnaces have been made. For example, in U.S. Pat. No. 3,078,173 to Dolph is disclosed a high alumina refractory brick containing a small percentage of an alkaline earth oxide. This improves resistance to aluminum penetration to some extent, but further improvement would be desirable. Moreover, since the alkaline earth oxides disclosed by Dolph react with phosphoric acid, the storage life of a phosphate-bonded high alumina refractory plastic or ramming mix is unsatisfactorily short.
It is an object of the present invention to provide a refractory for lining aluminum-melting furnaces and other containers for molten aluminum with improved resistance to metal penetration and to dross and metal adherence.
It is a further object of the present invention to provide a high alumina refractory that is phosphate-bonded and yet has a long storage life.
It is a further object of the present invention to provide such a refractory that is relatively inexpensive.
Other objects will be apparent from the following description of the invention.